Where did the "Magic Blood" of the Harry Potter Universe Originate From?

Question

What is a wizard that makes them non-Muggle? Or, more directly, what ancestry does the witch/wizard gene follow? Is there a patriarchal wizard (or matriarchal witch) that Muggles have no part in? Elves perhaps?

Stop reading here.

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Purpose of the Question/History/Don't Read

There seem to be solid consequences associated with being Muggle, or Muggle-related. A dominant theme in the novels is discrimination against the non-gifted race, but, when read into, the wizard bloodline doesn't appear all that well defined.

JKR indicates that wizard-ness is genetic, or inherited:

"Muggle-borns will have a witch or wizard somewhere on their family tree, in some cases many, many generations back. The gene resurfaces in some unexpected places."

By the above, it stands that a family that produces a squib (non-magical born of magical parents) must be a half-blooded family in some way, since half-blooded only requires one non-magical ancestor.

Of course, we are dealing in magic genetics. Any other form of genetics would make this inherited, seemingly recessive trait (or squibs couldn't exist), never appear at all. Unless they were XMen.

If it is so important, what does the wizard-bloodline follow?

Other Mythos

In other literature a wizard can be nearly anything, but magical powers are typically inherited as well as learned. Merlin of the Arthurian Legend (also mentioned in HP) is Cambian, meaning he is born of demonic intervention; this explains his source of enchantment.

Gandalf of Middle Earth is a Maiar, as are all Wizards of Middle Earth.

Wizards in Harry Potter seem to follow a bloodline, and it has been mentioned (in the question Gabe linked) that genetics have a heavy play in it, meaning that squibs and parents of Muggle-born wizards should have identical genetics. This bloodline must come from somewhere.

Magical Creatures

In Harry Potter it is common for magical creatures to "mingle" with humans, these beings are typically somewhat magical. Elves have been described to have very strong magic, but are for some unreasonable reason subservient to humans. I may be mistaken, but believe it was hinted that elves and the wizarding lineage had intersected at one time. Maybe I'm imagining this.

Genocidal Allusions

Voldemort hates muggles, and half-bloods, and whatever else is non-wizard.

The presence of this theme, suggests that this wizardly bloodline must be at least defined if the main antagonist is so obsessed with keeping that mysterious bloodline pure.

Since Slytherin himself was said to be a supremacist (circa a really long time ago) it suggests that this bloodline should have existed long before he was around, especially if he founded a school with people he was not related to, but were also magical.

Answer 1

I don't have a full answer, but can address the question about Salazar Slytherin and the (alleged) shared wizarding ancestor being long before him.

It's alluded to in the games canon (via Chocolate Frog cards in games) more than in the books, but there were clearly wizards all over the Ancient world:

• there are several Ancient Greek ones mentioned;

• it's noted that Goliath was a Giant mercenary though whether David was supposed to have been a wand bearer is not clear.

Given that wide ancient distribution, the magic lineage clearly must converge (if it converges at all) back to the original Cromagnon dispersal, to have been propagated to Proto-Indians as well as ancient semitic tribes.

Having said that, if magic has (as I think we established in the linked question) genetic basis, it's plausible that:

1. the relevant mutation(s) arose independently in a # of individuals

2. and/or the relevant mutation(s) may have predated modern hominids, as they are shared by other "magical" hominid - or may be even non-hominid - species (giants, elves, goblins, trolls) as well as non-ape magical creatures (kneazles, owls, Basilisks, spiders).

There is no clear canon support for this but it makes the most scientific sense.

Answer 2

I don't know if this will interest you, but here is a link to a great fan-written paper on wizarding genetics that just made the rounds a few weeks ago. From the author:

I read [J.K. Rowling's] statement that the wizarding gene is dominant. I have heard criticism that this does not explain muggle-borns, squibs, or the steady inheritance pattern of magical abilities; but I got your back. Magical ability could be explained by a single autosomal dominant gene if it is caused by an expansion of trinucleotide repeats with non-Mendelian ratios of inheritance.
(...)
[W]ithin a range, most muggles have about 50 trinucleotide repeats, but like any other trait there will be variation and some muggles might have 90 repeats and still be phenotypically non-magical. Muggle-borns are caused by spontaneous mutations.
(...)
There would be two genetic explanations for squibs. Either the individual did not inherit the wizarding gene despite TRD (explained in the next paragraph) or the individual has a rare deletion mutation removing a series of trinucleotide repeats.
(...)
[I]f my previous speculation about excessive trinucleotide expansions causing greater magical ability is correct, then these old wizarding families can accurately pride themselves in their unique genetics, since further trinucleotide expansions have likely occurred over many generations.
_{Kleonitz, Andrea - Wizarding Genetics - August 2012}

Included is discussion on the mutation factor of genetics, nature versus nurture, genetic anticipation, purebloods, half-bloods, Muggleborns, and Squibs. Note: this paper is a working hypothesis by a biology student. I wasn't sure what the protocol was for copying and pasting huge amounts of text from a research paper, so I erred against it and provided just a few short paragraphs. It's a really interesting read. I claim no responsibility for Tumblr :P

Wizarding Genetics by Andrea Kleonitz -- WARNING: Here be science ...

Answer 3

Wizards originate from Mars, Muggles from mushrooms.

From the Wizards of the Month section of J.K. Rowling's old website:

Hambledon Quince
1936 - present
Author of controversial theory that wizards originate from Mars, Muggles from mushrooms.

Of course, bear in mind that this is a controversial theory which likely hasn't been actually proven.